Thomas a



(No Model.)

T. A. EDISDN.

Electric Lamp.

No. 239,745. Patented April 5,1881.

' [lama/don .farneys.

:LPETERS. PHQTQ-LITNOGRAPHER, WASHINGTON. D C4 7 UNITED STATES PATENT OFFICE.

THOMAS A. EDISON, OF MENLO PARK, NEIV JERSEY.

ELECTRIC LAMP.

SPECIFICATION forming part of Letters Patent No. 239,745, dated April 5, 1881.

Application filed August 17, 1880.

To all whom it may concern:

Be it known that I, THOMAS A. EDISON, of Menlo Park, in the county of Middlesex and State of New Jersey, have invented a new and useful Improvementin Electric Lamps; and I do hereby declare that the following is a full and exact description of the same, reference being had to the accompanying drawing, and to the letters of reference marked thereon.

In electric lamps formed by sealing an incandescing conductor hermetically in a glass inclosing-globe, there maybe danger, sometimes, that the glass and wire will separate at the point where the comlucting-wires pass through and are sealed into the glass globe. This is due to the fact that the conductingwires, near the incandescing material, become very hot by conduction, and thatthccoetiicient of expansion of the glass and wire are so different.

In the lamps made on my plans, owing to the high resistance of the incandescing material, such small conductors are used that the danger referred to has been of minor or the very least importance. It may be desirable, however, to provide means which reduce the danger to a minimum, while aliording, at the same time, the necessary support for the very small and delicate conductors and incandescing material.

The object of this invention is to provide such means; and to that end it consistsin the features more particularly hereinafter sett'orth and claimed.

The drawing shows a lamp involving my invention.

A is the glass inclosing-globe, formed with tube a, for attachment to the exhausting apparatus. A smaller bulb, B, is made attached to the supporting-neck O, and formed with a tube, 1). Through the bulb B the conductors l 2 are passed and sealed therein, 1 being sealed ate 0, and 2 at e c. The bulb B is then sealed into A, at the line zz, and the tube 1) con- (No model) nected to the tube a, the bulb B practically forming the seal to A. The tube a is then connected to the exhaust apparatus. Itis evident that a vacuum 1s created in both A and B. \Vhen a proper degree of exhaustion is .reached the tube I) is sealed off at y, after which the tube a is sealed off at w. The vacuum in globe A is thus protected by two sealings of each wire, 0 c and c c, to only one set of which is there any danger, c 0, the other set, 0 e, from its distance from the heated portion of the. lamp, never heating sufficiently to be affected.

As very small conductors are used it is necessary, for stability, that they be supported near the carbon, which is done at the sealings 0'0,- butit'either otthese, from their proximity to the light, is ever so heated as to crack, it will still subserve its function as a support, while the vacuum is preserved by the sealsce.

\Vhat I claim is- 1. In an electric lamp, the combination, with the inclosing globe or-chamber, of a second chamber, through and into which the conducting-wires pass and are sealed, both chambers being hermetically secured together and exhausted, substantially as set forth.

2. The method of sealing the inclosing globe or chamber of an electric lamp, by sealing an exhausted auxiliary or secondary globe or chamber in the opening of the firstor inclosing globe, substantially as set forth.

3. The method of preserving the vacuum in the inclosing-globe of an electric lamp, consisting in sealing the conducting-wires at two points in a vacuum-globe hermetically sealed to thcinclosing-globc,substantially as sett'orth.

This specification signed and witnessed this 7th day of August, 1880.

THOS. A. EDISON.

Witnesses:

7M. OARMAN, Ocr'ro A. Moms. 

